An edge-type cutting tool implies a tool having one or more cutting elements (also termed points or edges) shaped as a solid of revolution, such as a disk or cup, adapted to rotate round their own axis by virtue of interaction with the workpiece being machined, or from a self-contained drive.
Methods of machining a workpiece with said tool are now known to be in widespread and common practical use, wherein a wear land is liable to occur on the tool relief surface in the course of machining, said wear land increasing incessantly as the cutting proceeds. Such as increase of the wear land results in a greatly raised value of the radial component of the cutting force applied and in an abrupt elevation of the temperature in the zone of cutting, which in turn reduces accuracy and quality of machining and causes vibration of the entire system "machine - tool - workpiece". Further enlargement of the wear land results in the tool losing its cutting properties so that the tool performs only rolling of the surface being machined. Thus, the formation of a wear land growing continuously in the course of machining, imposes a limitation upon a possibility of applying the rotary cutting tool, despite its high cutting efficiency, for machining large-sized workpieces under mass and large-lot production conditions since said tool requires repeated resharpening, whereas each of such resharpenings involves removal of the tool from the machine, setting it on a tool grinder to be resharpened and then setting the tool on the machine again, whereupon the latter is additionally set up for a required workpiece dimension. All this results in highly increased handling time spent in the course of machining workpieces and hence in sharply raised prime cost thereof.
It is a primary object of the present invention to provide a method of machining a workpiece with an edge-type rotary tool which would increase the accuracy of the workpieces being machined.
It is another object of the present invention to provide a method of machining a workpiece with an edge-type rotary tool which would improve the quality of the workpieces being machined.
It is one more object of the present invention to provide a method of the character set forth hereinbefore which would feature high cutting efficiency.
Said and other objects of the present invention are achieved in a method of machining a workpiece with an edge-type rotary tool, residing in the following: machining a workpiece is carried out concurrently with resharpening said cutting tool; said resharpening of said rotary cutting tool is applied to the relief surface of the edge thereof save the cutting lip so as to leave a wear land on the edge relief surface; the width of said wear land is maintained during the machining process within the limits selected to suit the tolerance margin adopted for the dimension of the workpiece being machined.
Thanks to the fact that the machining of the workpiece occurs concurrently with the tool resharpening process, handling time involved in the workpiece machining is sharply reduced and hence the efficiency of the proposed method is increased.
A favorable effect of such an engineering solution is that tool resharpening that keeps intact the cutting lip of the tool edge and leaves a preset wear land on the edge relief surface is conducive to retaining, for a prolonged period of time, a preset tool geometry without any resetting of the tool for the dimension of the workpiece being machined. This eventually adds to the accuracy and improves the quality of the workpiece being machined.
The width of the wear land is most expedient to be maintained within 0.01 to 1.0 mm.
A wear land less than 0.01 mm wide is scarcely attainable from engineering viewpoint, whereas such land having a width over 1.0 mm will not provide for chip removal from the workpiece being machined because of too high a repulsive component of the cutting force.
From a technological viewpoint tool resharpening may be carried out by a grinding tool fixed stationary which is most simple and easy to effect from a construction viewpoint and involves no special tool resharpening devices and attachments.
In order to increase higher efficiency of the rotary tool resharpening process use may be made of a rotary grinding tool.
Preferably, the grinding tool is imparted rotation from the edge-type rotary tool, which enables one to dispense with a special tool resharpening drive.
When finishing machining of workpieces requiring inconsiderable thickness of chip to be removed (within 0.05 mm), rotation of the grining tool is preferably transmitted from a self-contained drive, since too low a torque is in this case applied to the cutting tool.